This yarn is unique and rare! Boreray is the rarest of all British sheep. Spun from the soft undercoat of the Boreray and Soay breeds of sheep - two of the rarest sheep in Britain, along with some Shetland in early batches. These breeds hail from the remote islands of Boreray and Soay, in the St. Kilda archipelago out in the Atlantic Ocean, past the Outer Hebrides.